I know this is a very old issue but I haven't seen any solutions. Is there one?
This has happened on my Thinkpad X61s sporadically after upgrading from Vista x64 Ultimate to Windows 7 x64 Professional. There seemed to be a connection between motherboard temperature (hot after installing Win7 and updates) and the boot failure, but I am not 100% certain. It happened several times under various conditions including immediately after a successful full install and also after an install and OEM driver installation. Sometimes simply waiting and then restarting got it to boot. Other times not.
The boot would stall immediately after the first two dots of the logo appeared and then froze. Booting to safe mode showed that the boot stalled at classpnp.sys.
I tried all the usual stuff like system repair. No improvement. After letting the system settle(ie., cool) and also flashing the BIOS (it was very old), it hasn't happened again but I am worried. I see lots of references to this exact issue but so far no solutions. Someone always suggests a system repair, but after the OP reports that didn't solve it (it also didn't in my case) the thread continues with others saying they have the same issue and then just dies.
So.... has there been any progress determining why systems fail to boot, stalling at class.pnp.sys?